Field of the Invention
The invention relates to an electrically poorly conductive material for producing external glow-discharge protection for an electrical conductor having a high-voltage winding, the material including a base which is provided with a conductive coating on at least one side.
Such a material is disclosed in German Published, Prosecuted Patent Application 1 021 062. In that case, an electrically conductive silicone-rubber coating is applied to a base sheet web. The conductivity of that coating is achieved by additively mixing soot or graphite to the silicone-rubber which has not been vulcanized. A disadvantage of that known material is that a coating of the material must be wound 1/2-overlapped and must be vulcanized in order to produce an external glow-discharge protection for insulators with high rated voltages, which is costly and time-consuming.
German Published, Prosecuted Patent Application 1 092 529 discloses a further material for producing an insulating sleeve. In order to ensure improved external glow-discharge protection, a porous base material is used, which is made electrically conductive by impregnation with a solution of a suitable metal salt. Disadvantageously, that material cannot be used for production by machine using the total-immersion technique which can be carried out easily and cost-effectively.